The present invention relates generally to surface imagery and, more particularly, to photoprinting on metal or other substrates and to improvements in such photoprinting.
Processes of photoprinting on metal or other substrates are well known. Such processes involve several steps beginning with preparing a surface of the substrate, coating the prepared surface with a photographic emulsion, exposing the photographic emulsion coating to a desired image, treating the exposed photographic emulsion coating, and finally covering the treated surface with a protective coating.
The preparation of the surface of the substrate involves first thoroughly washing the surface, usually with water and/or ammonia water, air drying, and then applying thereto a solution of a polyurethane usually by spraying. After drying, a polyurethane coating thus formed is suitable for application thereto of the photographic emulsion. However, in the usual practice, this polyurethane coating possesses a yellowish tint which interferes in subsequent photographic steps. It is, therefore, an object of this invention to provide means for eliminating or masking this yellowish tint.